The following is an excerpt from the Explanatory Memorandum that is appended to the Regulations (at 21-22):
"4. The regulations seek to provide a framework governing all relevant aspects of MNP by –
a. laying down clear eligibility conditions for porting of mobile telephone numbers;
b. defining rights and obligations of various stake holders, i.e., the Donor Operator, the Recipient Operator, the MNP Service provider;
c. laying down the procedure to be followed by each player in the chain in processing number porting request;
d. specifying clear time limits for completion of various steps by each player in the chain i.e. the Donor Operator, Recipient Operator and the MNP service provider; and
e. envisaging least disruption of service to the consumer.
Salient features of the MNP under these regulations are as follows:
i MNP facility shall be available only within a given licensed service area.
ii A subscriber holding a mobile number is eligible to make a porting request only after 90 days of the date of activation of his mobile connection. If a number is already ported once, the number can again be ported only after 90 days from the date of the previous porting.
iii The Subscriber who wishes to port his mobile number should approach the Recipient operator (the operator to whom the subscriber wants to port his number). The Subscriber may be required to pay porting charges, if any, to the Recipient Operator.
iv The subscriber making the porting request is required to have cleared all the bills issued prior to the date of porting request. He shall give an undertaking that he has already paid all billed dues to the Donor Operator as on the date of the request for porting and that he shall pay dues to the Donor Operator pertaining to the mobile number till its eventual porting and that he understands and agrees that in event of non-payment of any such dues to the Donor Operator, the ported mobile number shall be liable to be disconnected by the Recipient Operator.
v A subscriber may withdraw his porting request within 24 hours of its submission to the Recipient Operator. However, the porting charges shall not be refundable.
vi The regulation envisage a maximum time period of four days for the completion of porting process.
vii Access Providers are required to implement All Call Query method.
viii The Originating operator shall be responsible to route the call to correct terminating network."

By India -- Telecommunications Regulatory Authority of India. Published January 2010.